Metal mirror based multispectral filter array

ABSTRACT

A device may include a multispectral filter array disposed on the substrate. The multi spectral filter array may include a first metal mirror disposed on the substrate. The multi spectral filter may include a spacer disposed on the first metal mirror. The spacer may include a set of layers. The spacer may include a second metal mirror disposed on the spacer. The second metal mirror may be aligned with two or more sensor elements of a set of sensor elements.

RELATED APPLICATION(S)

This application claims priority under 35 U.S.C. §119 to U.S.Provisional Patent Application No. 62/272,086, filed on Dec. 29, 2015the content of which is incorporated by reference herein in itsentirety.

This application claims priority under 35 U.S.C. §119 to U.S.Provisional Patent Application No. 62/294,970, filed on Feb. 12, 2016,the content of which is incorporated by reference herein in itsentirety.

BACKGROUND

A multispectral sensor device may be utilized to capture information.For example, the multispectral sensor device may capture informationrelating to a set of electromagnetic frequencies. The multispectralsensor device may include a set of sensor elements (e.g., opticalsensors, spectral sensors, and/or image sensors) that capture theinformation. For example, an array of sensor elements may be utilized tocapture information relating to multiple frequencies. A particularsensor element, of the sensor element array, may be associated with afilter that restricts a range of frequencies that are directed towardthe particular sensor element.

SUMMARY

According to some possible implementations, a device may include amultispectral filter array disposed on the substrate. The multispectralfilter array may include a first metal mirror disposed on the substrate.The multispectral filter may include a spacer disposed on the firstmetal mirror. The spacer may include a set of layers. The spacer mayinclude a second metal mirror disposed on the spacer. The second metalmirror may be aligned with two or more sensor elements of a set ofsensor elements.

According to some possible implementations, an optical filter mayinclude a first layer. The first layer may be a first mirror to reflecta portion of light directed toward the first layer. The first layer maybe deposited on a substrate associated with a set of sensor elements.The optical filter may include a second set of layers. The second set oflayers may be deposited solely on the first layer. The second set oflayers may be associated with a set of channels corresponding to the setof sensor elements. A channel, of the set of channels, may be associatedwith a particular thickness corresponding to a particular wavelength oflight that is to be directed toward a particular sensor element of theset of sensor elements. The optical filter may include a third layer.The third layer may be a second metal mirror to reflect a portion oflight directed toward the third layer. The third layer may be depositedon a plurality of the set of sensor elements associated with the secondset of layers.

According to some possible implementations, a system may include a setof optical sensors embedded into a substrate. The system may include amulti spectral filter array deposited on the substrate. Themultispectral filter array may include a first silver (Ag) metal mirror,a second silver (Ag) metal mirror, and a plurality of spacer layersdisposed between the first silver (Ag) metal mirror and the secondsilver (Ag) metal mirror.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram of an overview of an example implementationdescribed herein;

FIG. 2 is a diagram of an example process for fabricating a sensordevice with a multi spectral filter array;

FIGS. 3A-3C are diagrams of an example implementation relating to theexample process shown in FIG. 2;

FIGS. 4A-4C are diagrams of another example implementation relating tothe example process shown in FIG. 2;

FIGS. 5A and 5B are diagrams of another example implementation relatingto the example process shown in FIG. 2;

FIGS. 6A-6E are diagrams of another example implementation relating tothe example process shown in FIG. 2;

FIGS. 7A and 7B are diagrams of another example implementation relatingto the example process shown in FIG. 2;

FIGS. 8A and 8B are diagrams of another example implementation relatingto the example process shown in FIG. 2;

FIG. 9 is an example diagram relating to the example process shown inFIG. 2; and

FIGS. 10A and 10B are example diagrams relating to the example processshown in FIG. 2.

DETAILED DESCRIPTION

The following detailed description of example implementations refers tothe accompanying drawings. The same reference numbers in differentdrawings may identify the same or similar elements.

A sensor element (e.g., an optical sensor) may be incorporated into anoptical sensor device to obtain information (e.g., spectral data)regarding a set of electromagnetic frequencies. For example, the opticalsensor device may include a particular optical sensor, such as an imagesensor, a multi spectral sensor, or the like that may perform a sensormeasurement of light directed toward the particular optical sensor. Inthis case, the optical sensor may utilize one or more image sensortechnologies, such as an image sensor using a complementarymetal-oxide-semiconductor (CMOS) technology, an image sensor using acharge-coupled device (CCD) technology, or the like. The optical sensordevice may include multiple sensor elements (e.g., an array of sensorelements), each configured to obtain information. Additionally, oralternatively, the optical sensor device may include a set of sensorelements (e.g., optical sensors) configured to obtain a set of images,each associated with a different wavelength of light.

A sensor element may be associated with a filter that filters light tothe sensor element. For example, the sensor element may be aligned witha linear variable filter (LVF), a circular variable filter (CVF), aFabry-Perot filter, or the like to cause a portion of light directedtoward to the sensor element to be filtered. However, it may bedifficult to integrate a filter array using LVFs or CVFs or pattern afilter in association with a semiconductor. Moreover, some sets offilters, that are utilized for multispectral sensing, may be associatedwith relatively high angle shift values, relatively small spectralranges, or the like, which may reduce a spectral range of informationthat can be captured or an accuracy of information that is captured.

Implementations, described herein, may utilize an environmentallydurable filter array using metal mirrors for multispectral sensing. Inthis way, an optical filter may be provided for an optical sensor devicewith improved durability, improved spectral range, and reduced angleshift relative to one or more other types of filters. Moreover, adifficulty in incorporating a filter onto a semiconductor-based sensorelement or sensor element array may be reduced relative to one or moreother types of filters.

FIG. 1 is a diagram of an overview of an example implementation 100described herein. As shown in FIG. 1, a multispectral filter 105 (e.g.,a binary structure filter array) may include a first mirror 110-1, asecond mirror 110-2, and a spacer 120.

As further shown in FIG. 1, first mirror 110-1 and second mirror 110-2may sandwich spacer 120. In other words, spacer 120 may separate firstmirror 110-1 and second mirror 110-2 by a threshold distance, and/orfaces of spacer 120 may be enclosed by first mirror 110-1 and secondmirror 110-2. In some implementations, mirrors 110 may be associatedwith a particular material. For example, mirrors 110 may be depositedlayers of metal (e.g., silver). Mirrors 110 may align with each sensorelement of a sensor element array associated with each channel of themulti spectral filter array.

In some implementations, spacer 120 may include one or more spacerlayers 130. For example, spacer 120 may include a set of spacer layers130-1 through 130-5 (e.g., dielectric layers). In some implementations,a thickness of one or more layers 130 may be associated with ensuring aminimum spacer thickness for a particular wavelength.

In some examples, such as for a wavelength of 380 nanometers (nm) thatis directed toward one or more sensors, layer 130-1 may be associatedwith a thickness of 77.6 nm for a spacer material with a refractiveindex of 2.448 and an optical thickness of 190 nm. In this way, spacer120 ensures a minimum separation between mirrors 110 for a minimumwavelength of light that is to be directed toward one or more sensorelements. In some implementations, a thickness of one or more spacerlayers 130 may be related based on a binary progression. For example,spacer layer 130-2 may be associated with a thickness of approximately56.6 nanometers (nm), spacer layer 130-3 may be associated with athickness of approximately 28.3 nm, spacer layer 130-4 may be associatedwith a thickness of approximately 14.1 nm, and spacer layer 130-5 may beassociated with a thickness of approximately 7.1 nm.

In some implementations, multi spectral filter 105 may be deposited ontoa substrate associated with an optical sensor device. For example,mirror 110-1 may be deposited (e.g., via a deposition process and/or aphotolithographic lift-off process) onto a substrate that includes anarray of sensor elements to capture information (e.g., spectral data).In some implementations, spacer 120 may permit capture of informationrelating to multiple wavelengths. For example, a first portion of spacer120 aligned with a first sensor element (e.g., a back illuminatedoptical sensor or a front illuminated optical sensor of a sensor array)may be associated with a first thickness and a second portion of spacer120 aligned with a second sensor element may be associated with a secondthickness. In this case, light that is directed toward the first sensorelement and the second sensor element may correspond to a firstwavelength at the first sensor element based on the first thickness anda second wavelength at the second sensor element based on the secondthickness. In this way, multi spectral filter 105 permits multispectralsensing by an optical sensor device using a spacer (e.g., spacer 120)associated with multiple portions, which are associated with multiplethicknesses, aligned to multiple sensor elements of the optical sensordevice.

In some implementations, mirrors 110 may be associated with a protectivelayer. For example, a protective layer may be deposited onto mirror110-1 (e.g., between mirror 110-1 and spacer 120) to reduce a likelihoodof degradation of mirror 110-1, thereby improving durability of anoptical sensor device utilizing multi spectral filter 105. In someimplementations, mirrors 110 and/or spacer 120 may be associated with atapered edge. For example, as described herein, an edge portion ofmirror 110 and/or spacer 120 may be tapered and may permit another layer(e.g., a protective layer) to be deposited on the edge portion to reducea likelihood of degradation of the edge portion without obstructinganother portion of mirror 110 and/or spacer 120 (e.g., a non-edgeportion) associated with directing light toward an optical sensor,thereby improving durability of an optical sensor device utilizingmultispectral filter 105.

As indicated above, FIG. 1 is provided merely as an example. Otherexamples are possible and may differ from what was described with regardto FIG. 1.

FIG. 2 is a flow chart illustrating an example process 200 forfabricating an optical sensor device with a multispectral filter array,such as multispectral filter 105 shown in FIG. 1. Process 200 may beapplied to the design of an optical sensor device with a multispectralfilter array used to capture information relating to a spectralmeasurement. FIGS. 3A-3C are diagrams of an example implementation 300relating to example process 200 shown in FIG. 2.

As shown in FIG. 2, process 200 may include starting fabrication on anoptical sensor device (block 210). For example, as shown in FIG. 3A, andby reference number 304, a substrate 306 may include a set of sensorelements 308 embedded into substrate 306. In some implementations,substrate 306 may be associated with a particular composition. Forexample, substrate 306 may include a silicon-based substrate or thelike. In another example, substrate 306 may include a glass-basedsubstrate, and sensor elements 308 are disposed in a silicon-basedwafer, which is bonded to the glass-based substrate as described hereinin terms of FIGS. 8A and 8B. Additionally, or alternatively, substrate306 may be associated with a multispectral filter array that isassociated with a relatively low wavelength or spectral shift under arelatively high temperature condition (e.g., a heat tolerant filterarray).

In some implementations, substrate 306 may include one or moreconductive pathways (not shown) to provide information obtained by theset of sensor elements 308. For example, substrate 306 may include a setof conductive pathways permitting substrate 306 to be mounted to anotherdevice and provide data from the set of sensor elements 308 to the otherdevice, such as a camera device, a scanning device, a measurementdevice, a processor device, a microcontroller device, or the like. Insome implementations, substrate 306 may be associated with multiplelayers of substrate material. For example, substrate 306 may include amulti-layer substrate, a layer of which is associated with receiving theset of sensor elements 308.

In some implementations, substrate 306 may be associated with aparticular type of sensor element 308. For example, substrate 306 may beassociated with one or more photodiodes (e.g., a photodiode array), oneor more sensor elements of a sensor array coating or in a proximity toCMOS technology, CCD technology, or the like. In some implementations,substrate 306 may be associated with a set of back illuminated opticalsensors. In this case, substrate 306 may be thinner relative to anotherconfiguration, thereby permitting light to be directed through a siliconsurface toward the optical sensors.

As further shown in FIG. 2, process 200 may include depositing multiplelayers of a multispectral filter array onto a substrate associated withthe optical sensor device (block 220). For example, as further shown inFIG. 3A, and by reference number 310, a first mirror structure 312 maybe deposited onto substrate 306. In some implementations, first mirrorstructure 312 may be a single, solid metal mirror disposed in alignmentwith a set of sensor elements of the optical sensor device (e.g., sensorelements 308). In some implementations, first mirror structure 312 maybe associated with a uniform thickness. In some implementations, firstmirror structure 312 may be disposed within a threshold proximity ofsubstrate 306, such as onto an intermediate layer between substrate 306and first mirror structure 312. In other words, first mirror structure312 is not necessarily disposed onto substrate 306, but may be disposedonto an intermediate layer between substrate 306 and first mirrorstructure 312. In some implementations, mirror structure 312 may beassociated with a particular composition, such as a metallic composition(e.g., a metal mirror). For example, mirror structure 312 may utilize asilver (Ag)-based material, an aluminum (Al)-based material, a copper(Cu)-based material, or the like. In some implementations, mirrorstructure 312 may include a partially transparent material. For example,mirror structure 312 may permit a first portion of light (e.g., a firstwavelength band) to be directed toward the set of sensor elements 308and a second portion of light (e.g., a second wavelength band) to bere-directed away from the set of sensor elements 308. In someimplementations, mirror structure 312 and/or one or more other layersmay be deposited onto substrate 306 or onto another layer using a pulsedmagnetron sputtering deposition process, a lift-off process, or thelike. For example, a coating platform may be associated with depositingmirror structure 312 with a thickness of between 40 nm and 50 nm oranother similar thickness using a particular deposition process.Similarly, a coating platform may be associated with a particularsemiconductor wafer size (e.g., a 200 millimeter (mm) wafer or a 300 mmwafer), and may utilize a pulsed magnetron to perform deposition ofspacer layers, described herein, of a particular thickness (e.g., a lessthan 5 nanometers (nm) thickness, a less than 2 nm thickness, or a lessthan 1 nm thickness for some spacer layers and other thicknesses, suchas greater than 5 nm, greater than 50 nm, or greater than 100 nm forother spacer layers).

In some implementations, a set of spacer layers of a spacer may bedeposited to separate mirror structure 312 from another mirrorstructure. For example, as further shown in FIG. 3A, and by referencenumber 314, a first spacer layer 316 of a spacer may be deposited ontomirror structure 312 (e.g., using a pulsed magnetron sputteringdeposition process). In some implementations, first spacer layer 316 maybe deposited onto mirror structure 312 based on a patterning technique.For example, a lift-off process may be utilized to form first spacerlayer 316 with a particular thickness. First spacer layer 316 and/oranother spacer layer may be disposed completely onto mirror structure312. For example, first spacer layer 316 may include one or morediscrete portions that form a continuous spacer layer on a continuous,solid metal mirror. In this case, first spacer layer 316 and/or one ormore other spacer layers may form a plurality of channels aligned withthe set of sensor elements, which as a complete set of layers with firstmirror structure 312 and another mirror structure, described herein,direct light toward a corresponding plurality of sensor elements 308.

In some implementations, first spacer layer 316, in association withfirst mirror structure 312 and another mirror structure, describedherein, may be associated with performing a particular filteringfunctionality. In some implementations, based on a desired spectralrange (e.g., between approximately 380 nanometers and approximately 1100nanometers) or a desire for a reduced angle shift, first spacer layer316 and/or one or more other spacer layers may utilize an oxide-basedmaterial (e.g., niobium oxide, titanium oxide, tantalum oxide, or acombination thereof for a visible spectral range), a silicon-basedmaterial (e.g., silicon hydride (SiH) for a spectral range greater than650 nm, silicon carbide (SiC), or silicon (Si)), a germanium (Ge)-basedmaterial (e.g., for an infrared spectral range), or the like. In someimplementations, first spacer layer 316 may utilize a particularmaterial to achieve a reduction in angle shift relative to anothermaterial. For example, utilizing an Si—H based material may result in areduced angle shift relative to using a silicon-dioxide (SiO₂)-basedmaterial. In another example, first spacer layer 316 may utilize anothertype of oxide material, nitride material, fluoride material, or thelike.

As shown in FIG. 3B, and by reference number 318, a second spacer layer320 may be deposited onto first spacer layer 316. For example, secondspacer layer 320 may be deposited using a reactive magnetron sputteringprocess, a pulsed-magnetron sputtering process, an ion beam assisteddeposition process, an ion beam sputtering process, a dual ion beamsputtering process, a reactive direct current sputtering process, analternating current sputtering process, a radio frequency sputteringprocess, an atomic layer deposition process, or the like. Additionally,or alternatively, other depositions, described herein, such as forlayers 312, 316, 320, etc. may be similarly deposited. Althoughdescribed herein in terms of a particular order of deposition of layers,another order of deposition of layers may be utilized. In someimplementations, second spacer 120 may be associated with a thicknessrelating to first spacer layer 316. For example, when first spacer layer316 is associated with a first thickness to, second spacer layer 320 maybe deposited with a second thickness t₁. In some implementations, secondspacer layer 320 may be deposited onto a portion of first spacer layer316. For example, based on a desired spacer thickness arrangement for aset of channels (e.g., for a set of sensor elements 308 associated withthe set of channels), second spacer layer 320 may be deposited onto asubset of a surface of first spacer layer 316 to cause a first sensorelement 308 to be associated with a first spacer thickness and a secondsensor element 308 to be associated with a second spacer thickness,thereby permitting first sensor element 308 to capture informationassociated with a first wavelength and second sensor element 308 tocapture information associated with a second wavelength. For example, afirst layer may be deposited and may cover a set of sensor elements, asecond layer may be deposited and may cover half of the set of sensorelements, a third layer may be deposited and may cover a portion of theset of sensor elements, etc. Further details regarding patterning of aset of spacer layers are described with regard to FIGS. 4A-4C and FIGS.5A and 5B.

As further shown in FIG. 3B, and by reference number 322, a third spacerlayer 324 may be deposited onto second spacer layer 320 and/or firstspacer layer 316. For example, third spacer layer 324 and/or one or moresubsequent spacer layers (not shown) may be deposited. In someimplementations, third spacer layer 324 (and/or one or more other spacerlayers n, where n≧2) may be associated with half a thickness of aprevious layer (e.g., second spacer layer 320 for third spacer layer324). In other words, third spacer layer 324 may have a thickness of ½of the thickness of second spacer layer 320. In some implementations,third spacer layer 324 may be selectively deposited onto a portion offirst spacer layer 316 and/or second spacer layer 320. For example, afirst portion of third spacer layer 324 may be deposited onto a portionof first spacer layer 316 and a second portion of third spacer layer 324may be deposited onto a portion of second spacer layer 320, therebypermitting multiple sensor elements 308 to be associated with multiplespacer thicknesses and capture information associated with multiplewavelengths.

As further shown in FIG. 3B, and by reference number 326, a mirrorstructure 328 may be deposited. For example, mirror structure 328 may bedeposited onto one or more portions of one or more layers (e.g., firstspacer layer 316, second spacer layer 320, third spacer layer 324, oranother subsequent layer). In some implementations, mirror structure 328may be a solid, metal mirror disposed in alignment with optical sensorsof the optical sensor device (e.g., sensor elements 308). Based onspacer layers 316, 320, and 324 being deposited, mirror structure 328 isseparated from mirror structure 312 by a spacer. In this way, light maybe directed toward one or more sensor elements 308 at one or morewavelengths. In some implementations, another layer may be depositedbetween mirror structure 328 and spacer layer 324. For example, aprotective frame layer, a thin film layer, or the like may be depositedto perform one or more functionalities. As shown in FIG. 3C, beforedepositing lenses 330, an out-of-band blocker set of layers 332 (e.g., aset of layers forming a patterned blocker) may be deposited.Alternatively, an anti-reflective coating set of layers 334 may bedeposited. In some implementations, multiple discrete filter coatingsmay be deposited. Additionally, or alternatively, a single blocker maybe deposited to suppress out-of-band light for multiple wavelengths,multiple channels, or the like. In another example, a protective layermay be provided, such as a Zinc Oxide (ZnO) layer encapsulating thesilver of the mirror structures.

As further shown in FIG. 2, process 200, in some implementations, mayinclude depositing one or more other layers associated with the multispectral filter array (block 230). For example, a filter, such as ananti-reflective coating filter, an out-of-band blocking filter, ahigher-order suppression filter, or the like may be deposited, such asonto mirror structure 328, as described in detail, herein, with regardto FIGS. 7A and 7B and FIG. 9.

As further shown in FIG. 2, process 200 may include finalizing theoptical sensor device with the multi spectral filter array (block 240).For example, as further shown in FIG. 3B, and by reference number 326, aset of lenses 330 may be attached to mirror structure 328. For example,a particular lens 330, such as a glass lens, a plastic lens, or thelike, may be attached to mirror structure 328 to alter a characteristicof light that is directed toward a corresponding sensor element 308,such as to focus the light, distort the light, direct the light,increase an angle tolerance with which light may enter the opticalsensor device, increase an amount of light that is directed towardsensor element 308 of the optical sensor device, or the like.

In this way, a multispectral (e.g., a binary structure) Fabry-Perotfilter array may be constructed using metal mirrors. In someimplementations, an Nb₂O₅-based spacer or a TiO₂-based spacer may bepreferred for a visible spectral range. In some implementations, acombination of Nb₂O₅ and Si:H or TiO₂ and Si:H may be preferred for anear infrared (NIR) spectral range (e.g., from 750 nm to 1100 nm). Insome implementations, amorphous silicon or hydrogenated amorphoussilicon may be used. Additionally, or alternatively, based on utilizingAg-based metal mirrors, a relatively large spectral bandwidth may beachieved. Additionally, or alternatively, based on utilizing a pulsedmagnetron sputtering process and/or a liftoff process, the multispectralFabry-Perot filter array may be incorporated into an optical sensordevice with a semiconductor substrate without an excessive difficulty ofmanufacture.

Although FIG. 2 shows example blocks of process 200, in someimplementations, process 200 may include additional blocks, fewerblocks, different blocks, or differently arranged blocks than thosedepicted in FIG. 2. Additionally, or alternatively, two or more of theblocks of process 200 may be performed in parallel. As indicated above,FIGS. 3A-3C are provided merely as an example. Other examples arepossible and may differ from what was described with regard to FIGS.3A-3C.

FIGS. 4A-4C are diagrams of an example implementation 400 relating tothe example process 200 shown in FIG. 2. FIGS. 4A-4C show an example ofa filter array layout for a multispectral filter.

As shown in FIG. 4A, a filter array 401 may be associated with a set oflayers. Filter array 401 may be a 4×4 filter array including 16 channels(e.g., optical channels) corresponding to 16 sensor elements. In someimplementations, filter array 401 corresponds to the examplemultispectral filter 105 shown in cross-section in FIG. 1. In someimplementations, each channel may be associated with a sensor array. Forexample, a channel may include a sensor array with a set of sensorelements associated with capturing information regarding light directedfrom a light source using the channel. In some implementations, eachchannel may be associated with a particular thickness for each layer. Athickness of a set of layers of a channel may be selected based on adesired wavelength of information that is to be captured by an opticalsensor corresponding to the channel. In some implementations, the 4×4filter array (e.g., or another dimension filter array) may be associatedwith a particular patterning, such as a mosaic pattern (e.g., a snapshotBayer mosaic pattern), a tiled pattern (e.g., a snapshot tiled pattern),a line pattern (e.g., a continuous line-scan pattern or a discontinuousline-scan pattern), or the like.

Based on the spectral range that is to be captured by the opticalsensor, a thickness of a spacer layer sandwiched by mirrors of the 4×4filter array may be determined:

t _(max)=2*(λ_(max)/(4*n _(ref)));

t _(min)=2*(λ_(min)/(4*n _(ref)));

where t_(max) represents a total thickness of a spacer layer separatinga set of mirror structures for a highest center wavelength for whichinformation is to be captured, λ_(max) represents the highest centerwavelength for which information is to be captured, n_(ref) represents arefractive index of the spacer layer, t_(min) represents a totalthickness of a spacer layer separating a set of mirror structures for alowest center wavelength for which information is to be captured, andλ_(min) represents the lowest center wavelength for which information isto be captured.

A quantity of layers of the spacer layers that are to be deposited toform the set of channels (e.g., 16 channels of the 4×4 filter array) maybe determined:

c=2^(x);

where c represents a maximum number of channels that can be created fora given quantity of spacer layers that are deposited x. In someimplementations, less than a maximum quantity of channels may beselected for a particular quantity of spacer layers. For example,although a maximum of 16 channels may be created with a deposition of 4spacer layers, another quantity of channels may be selected for the 4spacer layers, such as 9 channels, 10 channels, or the like. In thiscase, one or more channels may be omitted or duplicated. For example,when a particular optical sensor is associated with poor performance forcapturing information regarding a particular wavelength, informationregarding the particular wavelength may be caused to be captured bymultiple optical sensors associated with multiple channels to improveaccuracy of the information.

A thickness for each layer of the spacer layers of a particular channel(e.g., for a set of equidistant channels) may be determined:

t ₀ =t _(min);

t ₁=(c/2)/((c−1)*2*n _(ref))*(λ_(max)−λ_(min));

t _(n) =t _(n-1)/2;

n=log₂(c);

where t_(n) represents a thickness of an nth layer (e.g., to is a firstlayer and t₁ is a second layer) and c represents a channel number for achannel of a set of channels. In some implementations, a set ofnon-equidistant channels may be utilized. For example, a discontinuouspatterning of channels may be selected to obtain information regarding afirst set of wavelengths and a second set of wavelengths that isdiscontinuous with the first set of wavelengths. In this case, t_(min)and t_(max) may still be determined, but a different set of intermediatelayers may be selected. In some implementations, a different quantity ofchannels may be utilized. Additionally, or alternatively, a patterningof channels may be utilized with multiple channels having a commonthickness, thereby permitting multiple optical sensors to captureinformation regarding a common wavelength of light.

As shown by reference number 402, filter array 401 includes a layer 402(e.g., of a spacer layer between a first mirror structure and a secondmirror structure), N, for which each channel is associated with aparticular thickness to cause a particular wavelength of light to bedirected toward a corresponding optical sensor. For example, a firstgroup of channels of layer 402 are associated with a thickness of 8*t₄,indicating that a layer of thickness 8*t₄ is deposited (where t₄represents a thickness of a fourth layer) (e.g., onto a first mirrorstructure or onto another layer, such as an oxide-based protective layerthat is deposited onto the first mirror structure). Similarly, a secondgroup of channels of layer 402 are associated with a thickness of 0*t₄,indicating that for these channels, deposition is performed, butlift-off is used to remove material that is deposited.

As further shown in FIG. 4A, and by reference number 404, a layer 404,N+1, is deposited onto layer 402. Layer 404 includes a first group ofchannels associated with a thickness of 4*t₄ and a second group ofchannels associated with a thickness of 0*t₄. In some implementations, athickness of layer 404 is selected based on a thickness of layer 402.For example, when manufacturing a multispectral filter (e.g., a filterassociated with a binary progression of filter layers), the thickness oflayer 404 may be selected as one half the thickness of layer 402. Inanother example, another relationship between layer 402 and layer 404may be utilized. For example, layer 404 may be 75% a thickness of layer402 and a subsequent layer may be 33%, 25%, etc. the thickness of layer404. In another example, layer 404 may be 50% a thickness of layer 402and a subsequent layer may be 33% a thickness of layer 404, 10% athickness of layer 404, or the like.

As further shown in FIG. 4A, and by reference number 406, a layer 406,N+2, is deposited onto layer 404. Layer 406 includes a first group ofchannels associated with a thickness of 2*t₄ and a second group ofchannels associated with a thickness of 0*t₄. As shown by referencenumber 408, a layer 408, N+3, is deposited onto layer 406. Layer 408includes a first group of channels associated with a thickness of 1*t₄and a second group of channels associated with a thickness of 0*t₄. Asshown by reference number 410, a thickness of layers N through N+3 isidentified for filter array 401 based on summing a thickness of eachlayer for each channel. For example, based on the binary progression andthe arrangement of filter layers, each channel may be associated with adifferent thickness, thereby permitting each corresponding opticalsensor to capture information regarding a different wavelength. Athickness of layer to (e.g., t_(min)) onto which t₁ to t_(n) aredisposed may be related to a wavelength of light regarding whichinformation (e.g., spectral data) is to be captured.

As shown in FIG. 4B, a similar filter array 421 may be associated with aset of layers, which are each associated with one or more thicknesses.As shown by reference number 422, a layer 422, M includes a first groupof channels associated with a thickness of 8*t₄ and a second group ofchannels associated with a thickness of 0*t₄. As shown by referencenumber 424, a layer 424, M+1, includes a first group of channelsassociated with a thickness of 4*t₄ and a second group of channelsassociated with a thickness of 0*t₄. As shown by reference number 426, alayer 426, M+2, includes a first group of channels with a thickness of2*t₄ and a second group of channels with a thickness of 0*t₄. As shownby reference number 428, a layer 428, M+3, includes a first group ofchannels with a thickness of 1*t₄ and a second group of channels with athickness of 0*t₄. As shown by reference number 430, a result ofdepositing layers 422, 424, 426, and 428 is a set of thicknesses for aset of channels of filter array 421, permitting optical sensors offilter array 421 to capture information relating to a set ofwavelengths.

As shown in FIG. 4C, another filter array 441 may utilize a lineararrangement of 16 channels rather than the 4×4 arrangement of filterarray 401 and filter array 421. As shown by reference number 442, alayer 442, L, includes a first group of channels with a thickness of8*t₄ and a second group of channels with a thickness of 0*t₄. As shownby reference number 444, a layer 444, L+1, includes a first group ofchannels with a thickness of 4*t₄ and a second group of channels with athickness of 0*t₄. As shown by reference number 446, a layer 446, L+2,includes a first group of channels with a thickness of 2*t₄ and a secondgroup of channels with a thickness of 0*t₄. As shown by reference number448, a layer 448, L+3, includes a first group of channels with athickness of 1*t₄ and a second group of channels with a thickness of0*t₄. As shown by reference number 450, a result of depositing layers442, 444, 446, and 448 is a set of thicknesses for a set of channels offilter array 441 to cause a set of optical sensors to captureinformation relating to a set of wavelengths.

As indicated above, FIGS. 4A-4C are provided merely as an example. Otherexamples are possible and may differ from what was described with regardto FIGS. 4A-4C.

FIGS. 5A and 5B are diagrams of an example implementation 500 relatingto the example process 200 shown in FIG. 2. FIGS. 5A and 5B show anexample of a filter array layout for a multispectral filter withnon-uniform channel spacing.

As shown in FIG. 5A, a filter array 501 (e.g., a multispectral filter)may utilize a non-equidistant channel layout. For example, as shown byreference numbers 502 through 508, layer 502 may include a group ofchannels with a thickness of 10*t4, layer 504 may include a group ofchannels with a thickness of 5*t4, layer 506 may include a group ofchannels with a thickness of 3*t4, and layer 508 may include a group ofchannels with a thickness of 1*t4. As shown by reference number 510, aresult of depositing layers 502, 504, 506, and 508 is a set ofthicknesses that are not equidistant for each channel. For example,channel 511 is associated with a thickness of 0*t4, channel 512 isassociated with a thickness of 1*t4, channel 513 is associated with athickness of 4*t4, and channel 514 is associated with a thickness of3*t4 (e.g., a channel associated with a thickness of 2*t4 is omitted).In this way, filter array 501 may permit a set of optical sensorsassociated with filter array 501 to capture information regarding anon-contiguous set of wavelengths (e.g., a set of wavelengths that arenot separated equidistantly).

As shown in FIG. 5B, a similar filter array 521 may utilize anothernon-equidistant channel spacing. For example, as shown by referencenumbers 522 through 528, layer 522 may include a group of channels witha thickness of 15*t4, layer 524 may include a group of channels with athickness of 4*t4, layer 526 may include a group of channels with athickness of 2*t4, and layer 528 may include a group of channels with athickness of 1*t4. As shown by reference number 530, a result ofdepositing layers 522, 524, 526, and 528 is a set of thicknesses for aset of channels that are not equidistant. For example, channel 531 isassociated with a thickness of 2*t4, channel 532 is associated with athickness of 6*t4, channel 533 is associated with a thickness of 21*t4,and channel 534 is associated with a thickness of 17*t4 (e.g., channelsof thickness 8*t4 through 14*t4, inclusive, are omitted). Adiscontinuity between channel 532 and channel 533 permits a set ofoptical sensors associated with filter array 521 to capture informationregarding two ranges of wavelengths separated by an amount of spectrumnot equal to a separation between other channels of filter array 521.

As indicated above, FIGS. 5A and 5B are provided merely as an example.Other examples are possible and may differ from what was described withregard to FIGS. 5A and 5B.

FIGS. 6A-6E are diagrams of an example implementation 600 relating tothe example process 200 shown in FIG. 2. FIGS. 6A-6E show an example ofan optical sensor device with a multi spectral filter.

As shown in FIG. 6A, substrate 602 may include one or more components.For example, substrate 602 may include a set of optical sensors 604,such as CMOS technology, CCD technology, or the like. A mirror 606(e.g., a metal-based reflector layer) may be deposited onto opticalsensors 604, and may permit a portion of light directed toward opticalsensors 604 to pass through mirror 606 toward optical sensors 604.Mirror 606 may be associated with a protective coating to reduceoxidization of mirror 606. For example, a zinc-oxide (ZnO)-basedmaterial may be coated onto a silver-based mirror, such as in aZnO/Ag/ZnO configuration, with a particular thickness of the ZnOcoating. For example, the ZnO coating may be an approximately 0.5 nm toapproximately 4 nm thickness, an approximately 1 nm thickness to anapproximately 2 nm thickness, or the like. A first spacer layer 608 of aspacer portion of the multi spectral filter may be deposited onto mirror606.

As shown in FIG. 6B, a second spacer layer 610 may be deposited onto aportion of first spacer layer 608 to cause a first group of channels ofthe filter array to be associated with a first thickness and a secondgroup of channels of the filter array to be associated with a secondthickness. In this case, second spacer layer 610 is deposited onto aportion of first spacer layer 608 aligned with optical sensors 604. Inthis way, a spacer of the multi spectral filter may be deposited tocause optical sensors 604 to receive light associated with a set ofbandwidths (e.g., a first bandwidth associated with the first thicknessor a second bandwidth associated with the second thickness).

As shown in FIG. 6C, in another example, a similar second spacer layer612 may be deposited onto a similar portion of first spacer layer 608 tocause a first group of channels of the filter array to be associatedwith a first thickness and a second group of channels of the filterarray to be associated with a second thickness. In this case, as shownby reference number 612, second spacer layer 612 is deposited to coveran edge of first spacer layer 608 and mirror 606 rather than only theportion of the first layer aligned with optical sensors 604.

As shown in FIG. 6D, and by reference number 620, the edge of firstspacer layer 608 and mirror 606 are protected by second spacer layer 612based on second spacer layer 612 being deposited to enclose both theportion of first spacer layer 608 aligned with optical sensors 604 andthe edge of first spacer layer 608 and mirror 606. In this way, secondspacer layer 612 provides an integrated protective frame (e.g., aprotective layer) for first spacer layer 608 and mirror 606, therebyreducing a likelihood that first spacer layer 608 and/or mirror 606 maybe damaged and increasing a durability of the optical sensor devicerelative to another optical sensor device with a filter array with anexposed mirror and/or an exposed coating of the mirror.

As shown in FIG. 6E, a similar substrate 602 may include a set ofoptical sensors 604, a first mirror layer 606 disposed in a particularproximity with substrate 602, and a first spacer layer 608 disposed ontofirst mirror layer 606. In this case, a zinc-oxide protective layer isdeposited to sandwich first metal mirror layer 606 in the particularproximity with substrate 602 thereby at least partially enclosing firstmetal mirror layer 606 and improving a durability of first metal mirrorlayer 602. A second spacer layer 622 is disposed onto a portion of firstspacer layer 608 (e.g., aligned to a subset of the set of opticalsensors 604 and/or pixels corresponding to the subset of optical sensors604). A frame 624 is disposed onto a portion of substrate 602, a portionof first spacer layer 608, and/or a portion of second spacer layer 620to provide a protective frame (e.g., a protective layer), therebyreducing a likelihood that substrate 602, mirror 606, first spacer layer608, and/or second spacer layer 622 may be damaged and increasing adurability of the optical sensor device. In this case, frame 624 isseparate from second spacer layer 622, thereby permitting frame 624 tobe constructed from a different material from second spacer layer 622,with a different thickness relative to second spacer layer 622, or thelike. In another example, second spacer layer 622 may be deposited in adifferent configuration, such as a configuration where second spacerlayer 622 is not deposited adjacent to or connected to frame 624 or thelike. For example, although edge 626 indicates that second spacer layer622 is adjacent to or partially enclosed by frame 624, second spacerlayer 622 may be spaced a particular distance from frame 624 such thatsecond spacer layer 622 is not adjacent to or partially enclosed byframe 624 at edge 626 or another edge.

As indicated above, FIGS. 6A-6E are provided merely as an example. Otherexamples are possible and may differ from what was described with regardto FIGS. 6A-6E.

FIGS. 7A and 7B are diagrams of an example implementation 700 relatingto the example process 200 shown in FIG. 2. FIGS. 7A and 7B show anexample of another filter associated with a multispectral filter array.

As shown in FIG. 7A, an optical sensor device 702 may include a set oflayers. Optical sensor device 702 may include a substrate 705 (e.g.,which may include one or more optical sensors), a first zinc-oxide layer710-1, a first silver mirror layer 715-1, a second zinc-oxide layer710-2, a niobium-titanium-oxide layer 720, a third zinc-oxide layer710-3, a second silver mirror layer 715-2, a fourth zinc-oxide layer710-4, a first silicon-oxide layer 725-1, a niobium-titanium-oxide layer730, and a second silicon-oxide layer 725-2. Zinc-oxide layers 710 aredeposited to at least partially enclose silver mirror layers 715,thereby protecting silver mirror layers 715 from degradation, therebyimproving durability of optical sensor device 702 relative to utilizingexposed mirror layers (e.g., one or more mirror layers depositeddirectly onto substrate 705 or niobium-titanium-oxide layer 720 or oneor more silver mirror layers 715 directly onto whichniobium-titanium-oxide layer 720 or first silicon-oxide layer 725-1 isdeposited). Optical sensor device 702 may include a first region 740(e.g., a multispectral filter array), which includes zinc-oxide layers710, silver mirror layers 715, and niobium-titanium-oxide layer 720.Optical sensor device 702 may include a second region 745, whichincludes silicon-oxide layers 725 and niobium-titanium-oxide layer 730.Layers of second region 745 may be deposited onto portions of region 740to provide a filtering functionality for optical sensor device 702. Forexample, second region 745 may provide an anti-reflective coating foroptical sensors of optical sensor device 702.

As shown in FIG. 7B, a similar optical sensor device 702 includes asubstrate 705, a similar region 740 (e.g., a similar multispectralfilter array), and a set of silicon-oxide layers 750 (shown as 750-1through 750-5) and a set of niobium-titanium-oxide layers 755 (shown as755-1 through 755-4). In this case, a region 760, which includes the setof silicon-oxide layers 750 and the set of niobium-titanium-oxide layers755 may provide higher order suppression of certain wavelengths (e.g.,ultraviolet (UV)-green wavelengths). In this way, a filteringfunctionality may be added to a multispectral filter array by depositingone or more other layers onto the multispectral filter array.

As indicated above, FIGS. 7A and 7B are provided merely as an example.Other examples are possible and may differ from what was described withregard to FIGS. 7A and 7B.

FIGS. 8A and 8B are diagrams of an example implementation 800 relatingto example process 200 shown in FIG. 2.

As shown in FIG. 8A, sensor elements 308 may be disposed in substrate306 during manufacture of an optical sensor device described herein. Aglass wafer 802 may be provided, onto which a set of filter and spacerlayers may be deposited, as described herein.

As shown in FIG. 8B, after depositing a set of layers 804 onto glasswafer 802, glass wafer 802 and layers 804 are bonded to substrate 306,as shown by reference number 806. In this way, layers can be formed on aseparate substrate from sensor elements 308 and attached to sensorelements 308.

As indicated above, FIGS. 8A and 8B are provided merely as an example.Other examples are possible and may differ from what was described withregard to FIGS. 8A and 8B.

FIG. 9 is an example of a diagram 900 of a transmissivity (as apercentage of light) relative to wavelength (of the light in nm). FIG. 9shows a spectral response of a filter stack, described herein withregard to FIG. 7B, for suppressing higher order peaks at lowerwavelengths, as indicated by reference number 905. For example, when alarge spectral bandwidth is to be covered, as shown, and a particularsubset of the spectral bandwidth is to be passed, such as at 850 nm, abandpass filter, as described with regard to FIG. 7B, may be provided toblock higher order peaks at 350 nm and 450 nm and may exhibit spectralperformance similar to diagram 900.

As indicated above, FIG. 9 is provided merely as an example. Otherexamples are possible and may differ from what was described with regardto FIG. 9.

FIG. 10A are example diagrams 1000 and 1010 of a 64 channel filter arrayusing a silver based mirror and a niobium-titanium-oxide based spacer,as described herein. FIG. 10A shows a spectral range of each sensorelement of the 64 channel filter array based on a corresponding filterportion. FIG. 10B shows a center wavelength for each sensor element ofthe 64 channel filter array based on a corresponding filter portion. Inthis case, each sensor element is centered at a different wavelength. Inanother example, multiple sensor elements may be centered at a commonwavelength.

As indicated above, FIG. 10 is provided merely as an example. Otherexamples are possible and may differ from what was described with regardto FIG. 10.

In this way, a multi spectral filter array may be fabricated for anoptical sensor device that is integrated onto a semiconductor substrateof the optical sensor device, provides relatively low angle shift,relatively high spectral range, and is environmentally durable relativeto other filter structures.

The foregoing disclosure provides illustration and description, but isnot intended to be exhaustive or to limit the implementations to theprecise form disclosed. Modifications and variations are possible inlight of the above disclosure or may be acquired from practice of theimplementations.

Some implementations are described herein in connection with thresholds.As used herein, satisfying a threshold may refer to a value beinggreater than the threshold, more than the threshold, higher than thethreshold, greater than or equal to the threshold, less than thethreshold, fewer than the threshold, lower than the threshold, less thanor equal to the threshold, equal to the threshold, etc.

Even though particular combinations of features are recited in theclaims and/or disclosed in the specification, these combinations are notintended to limit the disclosure of possible implementations. In fact,many of these features may be combined in ways not specifically recitedin the claims and/or disclosed in the specification. Although eachdependent claim listed below may directly depend on only one claim, thedisclosure of possible implementations includes each dependent claim incombination with every other claim in the claim set.

No element, act, or instruction used herein should be construed ascritical or essential unless explicitly described as such. Also, as usedherein, the articles “a” and “an” are intended to include one or moreitems, and may be used interchangeably with “one or more.” Furthermore,as used herein, the term “set” is intended to include one or more items(e.g., related items, unrelated items, a combination of related items,and unrelated items, etc.), and may be used interchangeably with “one ormore.” Where only one item is intended, the term “one” or similarlanguage is used. Also, as used herein, the terms “has,” “have,”“having,” or the like are intended to be open-ended terms. Further, thephrase “based on” is intended to mean “based, at least in part, on”unless explicitly stated otherwise.

What is claimed is:
 1. A device, comprising: a multispectral filterarray disposed on a substrate, the multispectral filter array including:a first metal mirror disposed on the substrate, a spacer disposed on thefirst metal mirror, the spacer including a set of layers, a second metalmirror disposed on the spacer; and wherein the second metal mirror isaligned with two or more sensor elements of a set of sensor elements. 2.The device of claim 1, where the first metal mirror has a uniformthickness over the set of sensor elements.
 3. The device of claim 1,where the second metal mirror is aligned with all of the set of sensorelements.
 4. The device of claim 1, where the set of layers comprises: aset of spacer layers, a first layer of the set of spacer layerscorresponding to a first channel, of a set of optical channels alignedto the set of sensor elements, and being associated with a firstthickness, and a second layer of the set of spacer layers correspondingto a second channel, of the set of optical channels, and beingassociated with a second thickness that is different than the firstthickness, the first layer covering a first quantity of sensor elementsof the set of sensor elements, the second layer covering a secondquantity of sensor elements of the set of sensor elements, the secondquantity being half the first quantity.
 5. The device of claim 1, wherethe first metal mirror and the second metal mirror include at least oneof: a silver (Ag)-based mirror, an aluminum (Al)-based mirror, or acopper (Cu)-based mirror.
 6. The device of claim 1, where the spacerincludes at least one of: an amorphous silicon-based material, ahydrogenated amorphous silicon (Si:H)-based material, a germanium(Ge)-based material, a niobium-oxide (Nb₂O₅)-based material, atitanium-oxide (TiO₂)-based material, a tantalum-oxide (Ta₂O₅)-basedmaterial, a silicon-oxide (SiO₂)-based material, an yttrium-oxide(Y₂O₃)-based material, a zirconium-oxide (ZrO₂)-based material, analuminum-oxide (Al₂O₃)-based material, a silicon-nitride (Si₃N₄)-basedmaterial.
 7. The device of claim 1, where one or more layers of themultispectral array are deposited layers, the deposited layers beingdeposited on the substrate using a pulsed magnetron sputtering process.8. The device of claim 1, where the set of sensor elements furthercomprise at least one of: a photodiode array, a charge-coupled device(CCD), or a complementary metal-oxide-semiconductor (CMOS).
 9. Thedevice of claim 1, where the multi spectral filter array furtherincludes: a first set of zinc (Zn) oxide protective layers sandwichingthe first metal mirror; and a second set of zinc (Zn) oxide protectivelayers sandwiching the second metal mirror.
 10. The device of claim 1,further comprising: one or more filter layers disposed on themultispectral filter array to filter light directed to the set of sensorelements, the one or more filter layers including at least one of: anout-of-band blocking set of layers, an anti-reflective coating set oflayers, or a higher order suppression set of layers.
 11. The device ofclaim 1, further comprising: a set of lenses disposed on themultispectral filter array, a particular lens, of the set of lenses,being associated with directing light toward a particular opticalsensor, of the set of sensor elements, via a channel of the multispectral filter array.
 12. An optical filter, comprising: a first layer,the first layer being a first mirror to reflect a portion of lightdirected toward the first layer, the first layer being deposited on asubstrate associated with a set of sensor elements; a second set oflayers, the second set of layers being deposited solely on the firstlayer, the second set of layers being associated with a set of channelscorresponding to the set of sensor elements, a channel, of the set ofchannels, being associated with a particular thickness corresponding toa particular wavelength of light that is to be directed toward aparticular sensor element of the set of sensor elements; and a thirdlayer, the third layer being a second metal mirror to reflect a portionof light directed toward the third layer, the third layer beingdeposited on a plurality of the set of sensor elements associated withthe second set of layers.
 13. The optical filter of claim 12, where aspectral range of light that is directed toward the set of sensorelements when the optical filter is exposed to a light source is betweenapproximately 380 nanometers and approximately 1100 nanometers.
 14. Theoptical filter of claim 12, where the first layer having been depositedon the substrate via a pulsed magnetron sputtering process.
 15. Theoptical filter of claim 12, where at least one of the first layer or thethird layer includes a first oxide-based protective layer, a metal-basedreflector layer, and a second oxide-based protective layer, themetal-based reflector layer being sandwiched between the firstoxide-based protective layer and the second oxide-based protectivelayer.
 16. A system, comprising: a set of optical sensors embedded intoa substrate; and a multispectral filter array deposited on thesubstrate, the multispectral filter array including: a first silver (Ag)metal mirror, a second silver (Ag) metal mirror, and a plurality ofspacer layers disposed between the first silver (Ag) metal mirror andthe second silver (Ag) metal mirror.
 17. The system of claim 16, wherethe set of optical sensors are a plurality of optical sensors of a superarray.
 18. The system of claim 16, where the set of optical sensors areassociated with receiving a portion of light from a light source. 19.The system of claim 16, where the set of optical sensors is a backilluminated sensor array.
 20. The system of claim 16, where theplurality of spacer layers comprise a material selected to reduce anangle shift of light directed from a light source toward the set ofoptical sensors.